Treatment of wood



Patented Nov. 21, '1933 UNITED STATES 'rnnamnr oF woon can n. siever,oak Puk, m, Application october s, 1930. serial Nu. 486,718

-2Claims.

My present invention relates to improvements in the treatment Vof woodand has to do particularly with method of and means for preventing thecracking of Wooden timbers.

i The treatment of wooden timbers such as railroad crossties and thelike, to prolong the life thereof, is becoming of more and more impor'-tance as time goes on, and the supply of Wood diminishes. It is safe toassume that at least l@ 90% of the wood used for' railroad crossties issubjected to some kind of preservative treatment before it is used. Withthe best treatment available, the useful life of the crosstie is ofcourse increased, but still it is only a matter of a few ld added yearsbefore the tie is permanently out of service.

One of the principal causes of the relatively rapid deterioration ofwood, particularly heavy wood such as crossties, when used outside, is

2Q the cracking Ywhich takes place due to exposure to the weather andthe like. nating treatment extends only a fraction of an inch, or aninch at most, below the surface, a crack not only admits water andcauses a rapid deterioration in the tie from a mechanical standpoint,but it admits fungi to the central, untreated portions of the tie whererelatively rapid propagation takes place, and the tie ,issoon rendered yunfit for use. Accordingly, if railroad ties and 3o similar woodentimbers are to be given a long useful life, they must be treated eitherto prevent cracking, or to cause such a thorough and deep impregnationthat even though the wood does crack, no fertile field for the lodgmentof fungi will be found.

The principal object of my present invention is to prevent the crackingof wooden timbers.

i Another, but incidental object, is to secure a more thoroughimpregnation of the wooden 4o timber. y

Another object is the production of a wooden member such as a crosstiewhich will have a long and useful life.

Other objects and features of the invention will be apparent from aconsideration of the following detailed description taken with theaccompanying drawing, wherein, j

Fig. 1 is a fragmentary sectional view showing a crosstie treated inaccordance with my present invention, and,

Fig. 2 is a sectional view taken along the line 2--2 of Fig. 1.

Referring generally to the invention first, I prepare the tie by formingopenings, preferably longitudinal and continuous openings, and then thanfrom the interior.

Since the impregimpregnate the ties, including the area of the openingsin the most approved fashion, andthis method when properlyl controlled,produces a tie which will not crack appreciably under the most l severeconditions. In order that those skilled in l0 the art may fullyunderstand the invention, however, I shall describe the same in detail,including certain explanations which appear to clarify the situation,but by which I do not bind myself, as of course, the explanation for thebehavior of the tie may be incorrect.

First, as to the reason for the cracking, it appears that when timber-which contains a relatively high percentage of/'moisture is subjectedto a rapid drying process, moisture is driven from the surface thereof`a great deal more rapidly This causes a shrinking of the timber on thesurface, thereby bringing `up strains and stresses which are relievedonly by the fracturing of the-surface, resulting in a crack. It appearsthat this condition might be corrected by slow, controlled drying of thetimber, but this is neither commercially practicable nor positivetreatment. -It appears that by forming openings `through the timber andthen impregn 'ating it, as carried out by me, an equilibrium isestablished which is not disturbed or. modied by subsequent conditionsdevolping in the timber during its useful life.

In the specific steps in carrying out my procese,

I select a standard type of tie, freshlycut, and

before cracking strains have been setup therein, and form a number ofopenings 10 therethrough,

vpreferably as shown in Fig. 1. These openings are shown as. five innumber, but they may have any shape and distribution desired. In actualpractice, ve round openings one-half inch in diameter and extending fromone end to the other of the timber are adequate. l

The next step in the preferred c out of the process is `the furtherpartial drying of the wood, which is preferably vcarried on tosubstantially what is known as the ber saturationv poin although thetimber is not necesa sarily reduced to this state of dryness. I wish topoint out here that as far as the drying of the timber is concerned,this may be varied within a considerable range, and all of the dryingmay take place before the holes are bored, and preferably, sorne shouldtake place before the-boring A of the goles, particularly if the wood isunusually et. Those acquainted with the treatment and handling of woodwill understand that the timberv should be dry `enough to make theboring of the holes a relatively simple matter,

but under no circumstances should the timber be so dry that crackingtakes place.

After the boring of the holes and when the timber has reached its properstate of dryness, it is impregnated in such a Way as to expose the areaof the openings to the impreginating liquid. In the preferred practiceof the invention heat and pressure are used as now generally carried onin pressure tanks. I prefer the use of creosote for impregnation, or amixture of creosote and other substances, as shown in my copendingapplication, Serial Number 486,717,l led October 6, 1930. When thetimber has been thoroughly impregnated, it is removed from theimpregnating liquid, care being taken to keep the openings lled with theimpregnating liquid. This is done preferably by corking up both ends ofthe opening. preferably with creosoted wooden plugs 1l which are driveninto place and retained there during theentire life of the timber.

I have found that timbers treated in this way will not crack under themost extreme and rigorous tests. In order to compare the productproduced by my process with timbers treated in other ways, I carried outthe following experiments: v

First, I took tive sets of four timbers each and bored three sets ofthem as shown in the attached drawing. The rst drilled set was thenfurther treated in accordance with the process outlined above, using hotcreosote at pressure varying from 150 to 200 pounds for approximatelyfive hours. The second set of four drilled Wooden pieces was treated inthe same way, except that the openings or canals therethrough wereimpregnated with hot petroleum oil, from which the more volatileconstituents had been removed. The third set of four drilled woodenpieces was left unplugged and treated in a hot creosote bath for ilvehours at atmospheric pressure and at a temperature of 180 degreesFahrenheit. The fourth set of wooden pieces was undrilled but subjectedto the same creosote treatment as the third set. The fifth set ofundrilled pieces received no treatment whatsoever. As a test, all oi thesamples were stored for a long period of time, two of each set ofsamples being rst soaked in water for a relatively long period of time,and then subsequently aged in the open. This included cold Winterweather with ice, etc., at which time considerable damage is always doneto exposed Wood. Spikes were also driven through all of the woodenpieces in places to determine what eilect, if any, the presence ofspikes would have upon the cracking of the timbers. v

At the end of the test period all of the undrilled wooden pieces, bothdry and water soaked, were very badly cracked, the cracking in somecases extending entirely through the wood and substances.

passing through the spike holes. The water soaked pieces, however, werefound to be cracked the worst. All of the drilled pieces which had beenimpregnated at atmospheric pressure showed cracks at the nail holes (thewater soaked pieces being the worst) but no appreciable cracking inother places. None of the drilled samples which had been impregnatedinternally under pressure were cracked,` regardless of whether or notthey had been previously Water soaked. This was true both of samples 1and 2, namely, those treated with creosote and those treated internallywith petroleum oil. It is obvious therefore, that the treatment byinternal impregnation under pressure has a definite value in preventingcracking of wood when the latter is exposed to outdoor Weatherconditions.

The cross-sectional view shown in Fig. 2 illustrates in general, theaction of the impregnating substances. impregnation takesv place at theusual depth both on the side and surfaces of the openings, as shown bythe shading in Fig. 2. When Water-proofing material such as creosote issealed into the interior of the tie it gradually penetrates as timepasses as shown by the light 10@ shaded portions, sothat ultimately,substantially complete impregnation therethrough results.

Those skilled in the art will understand that the details given aboveare illustrative, and that the invention may take other forms. Forexample, I am not limited to an particular number, size and shape ofholes orcanals in the timbers, but may use any number which the size ofthe timber may require, and the size and cross shape of the holes may bevaried. While I refer to wood 11@ in the claims, the process can be usedon any cellulosic substances of vegetable origin, and the term wood isused broadly to include all of such As to the Wood treating material,this may be a waterproong substance alone, or it may contain added toxicsubstances, illustrated in my copending application referred tohereinabove.

What I claim is new and desire to protect by l Letters Patent of theUnited States is:- 12@ 1. The method of treating wooden timbers toprevent cracking thereof, which consists in forming canals in thetimbers, drying the timbers, impregnating the timbers with awaterproofing liquid under heat and pressure, and then closing the endsof the canals to conne some of the liquid therein.

2. The method of treating wooden timbers to prevent cracking thereof,which consists in forming canals in the timbers, impregnating thetimbers with creosote with heat and pressure, andsealing the ends of thecanals so as to conne a portion of creosote therein.

CARL H. SIEVER..

